In recent years, a hollow golf club head has been proposed in which not only its face portion but also its crown portion elastically deforms, when hitting a ball, to increase the launch angle, so as to increase the traveling distance. For example, Japanese Patent Laid-Open Nos. 2003-79768 and 2005-211438 disclose such a golf club head in which the rigidity of a crown portion is decreased.
A golf club head described in Japanese Patent Laid-Open No. 2003-79768 comprises a metal-made hollow golf club head having at least a face portion, sole portion, side portion, and crown portion. A metal material that forms the crown portion has the lowest modulus of longitudinal elasticity.
A golf club head described in Japanese Patent Laid-Open No. 2005-211438 comprises a metal-made hollow golf club head having at least a face portion, sole portion, side portion, and crown portion. Metal materials that form the crown portion and at least the upper portion of the side portion have the lowest modulus of longitudinal elasticity.
The golf club heads described in Japanese Patent Laid-Open Nos. 2003-79768 and 2005-211438 still have room for improvement in terms of increasing the launch angle and improving the rebound property when hitting a ball. In addition, in the golf club heads described in Japanese Patent Laid-Open Nos. 2003-79768 and 2005-211438, when the rigidity of a crown portion is decreased, the hitting impression sometimes get worse and the hitting sound sometimes becomes lower.